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>Are there any inherently stable/noise free/non-Volatile Quantum Computing methods, at all? No, but there are methods (quantum error correction) that allow you

>Are there any inherently stable/noise free/non-Volatile Quantum Computing methods, at all? No, but there are methods (quantum error correction) that allow you to simulate noise free qbits with multiple, slightly noisy qbits. The main challenge here is that you need to start with quite good qbits for this error correction to actually help.

naasking 4y ago
My prediction: it will never scale properly.
- sebzim4500 4y ago
  Not disagreeing necessarily but why do you think this? Codes have got better, qbits have got massively better over the last few decades, why wouldn't the two lines eventually cross? Do you think there is some physical principle that will prevent getting a quantum speedup, or do you just think that the practical engineering challenges are simply too difficult?
  - naasking 4y ago
    I've become increasingly convinced that QM is incomplete for various reasons, and so I no longer have confidence that coherence will scale the way we expect. I think it will hit a hard limit that we can't yet see because of this incompleteness. Maybe that wall will become clear once we have quantum gravity, maybe some successor to QM like [1] will clarify what's happening. [1] https://arxiv.org/pdf/2102.07795.pdf https://arxiv.org/pdf/2102.07795.pdf
    - sebzim4500 4y ago
      If there is a phsyical principle that stops QCs from working, then trying to build QCs is probably the best way to make progress in fundamental physics.
      - naasking 4y ago
        Yes, quantum computers are good physics research in the same way that ITER can be considered good plasma research. Neither will produce a working product that some people are expecting. I'm not sure that QC will discover the problem before we infer it theoretically due to the many engineering challenges, but it's possible. If any real progress is made in QC, my bet's on boson sampling.
      - bawolff 4y ago
        Yeah, seems very win-win. Either we get a working quantum computer or we make revolutionary new discoveries in physics. Either option would be pretty exciting.
    - ko27 4y ago
      Isn't the paper mentioned in the article literally proving that wrong? Google managed to scale error correction and achieved less noisy qbits.
      - naasking 4y ago
        Sure, they scaled it in the same way we're able to build bigger and more effective rockets than 50 years ago. We'll never travel faster than light though, because the speed of light is known to be the limit. I'm saying there will be some ultimate limit to coherence as well, but quantum mechanics is incomplete as a model of reality so we just don't see that in the math yet.
        gloriousduke 4y ago
        If that's the case, the QC computer endeavors are still worthwhile since while failing to scale them we may develop another piece of a more complete model of reality.
    - parton 4y ago
      Could you briefly summarize one of the reasons you think QM is incomplete? I would agree with you that there is no reason to expect coherence to scale, but I don't know of any reason for it not to scale either.
      - naasking 4y ago
        Nobody knows of any certain reasons to not scale, but there's plenty of speculation. Someone else posted about Gil Kalai in this subthread, so he's one high profile person that has documented his skepticism on quantum computing and explained his reasons. For my part, I don't think quantum foundations are on a firm footing. I think the measurement problem is still unresolved to a satisfactory degree, which means our understanding of decoherence is incomplete. Per the link I posted above, there's also a good chance that gravity is inherently decoherent, which means entanglement will naturally breakdown in various conditions around mass. I've also developed skepticism of quantum field theories. For one, the supposedly "most precise calculation in physics" has been marred by numerous mistakes and even fraud (electron magnetic moment). Renormalization is also sketchy business. A more fringe reason, but one I think will resolve some of those issues is a growing skepticism of continuity [1], even for classical mechanics; continuous formalisms just seem to lead to logical and physical absurdities, like Norton's Dome and singularities in GR. Discrete theories are only now getting a little attention, but they're promising [2] because they seem to eliminate some of the formal structure (gauges), and the infinities disappear. [1] https://arxiv.org/abs/1609.01421 https://arxiv.org/abs/1609.01421 [2] https://arxiv.org/abs/1902.08997 https://arxiv.org/abs/1902.08997
  - klyrs 4y ago
    Here's a well-informed argument to that end: https://arxiv.org/abs/1908.02499 https://arxiv.org/abs/1908.02499 and a nuanced lay-opinion by the same author: https://gilkalai.wordpress.com/2022/05/26/waging-war-on-quantum/ https://gilkalai.wordpress.com/2022/05/26/waging-war-on-quan...
  - sampo 4y ago
    > qbits have got massively better over the last few decades Progress has been rather slow: 2001: Shor's algorithm was used to factor 15 2012: Shor's algorithm was used to factor 21 2019: Shor's algorithm was attempted at factoring 35, but failed due to too much error accumulation

naasking 4y ago

My prediction: it will never scale properly.

sebzim4500 4y ago
Not disagreeing necessarily but why do you think this? Codes have got better, qbits have got massively better over the last few decades, why wouldn't the two lines eventually cross? Do you think there is some physical principle that will prevent getting a quantum speedup, or do you just think that the practical engineering challenges are simply too difficult?
- naasking 4y ago
  I've become increasingly convinced that QM is incomplete for various reasons, and so I no longer have confidence that coherence will scale the way we expect. I think it will hit a hard limit that we can't yet see because of this incompleteness. Maybe that wall will become clear once we have quantum gravity, maybe some successor to QM like [1] will clarify what's happening. [1] https://arxiv.org/pdf/2102.07795.pdf https://arxiv.org/pdf/2102.07795.pdf
  - sebzim4500 4y ago
    If there is a phsyical principle that stops QCs from working, then trying to build QCs is probably the best way to make progress in fundamental physics.
    - naasking 4y ago
      Yes, quantum computers are good physics research in the same way that ITER can be considered good plasma research. Neither will produce a working product that some people are expecting. I'm not sure that QC will discover the problem before we infer it theoretically due to the many engineering challenges, but it's possible. If any real progress is made in QC, my bet's on boson sampling.
    - bawolff 4y ago
      Yeah, seems very win-win. Either we get a working quantum computer or we make revolutionary new discoveries in physics. Either option would be pretty exciting.
  - ko27 4y ago
    Isn't the paper mentioned in the article literally proving that wrong? Google managed to scale error correction and achieved less noisy qbits.
    - naasking 4y ago
      Sure, they scaled it in the same way we're able to build bigger and more effective rockets than 50 years ago. We'll never travel faster than light though, because the speed of light is known to be the limit. I'm saying there will be some ultimate limit to coherence as well, but quantum mechanics is incomplete as a model of reality so we just don't see that in the math yet.
      - gloriousduke 4y ago
        If that's the case, the QC computer endeavors are still worthwhile since while failing to scale them we may develop another piece of a more complete model of reality.
  - parton 4y ago
    Could you briefly summarize one of the reasons you think QM is incomplete? I would agree with you that there is no reason to expect coherence to scale, but I don't know of any reason for it not to scale either.
    - naasking 4y ago
      Nobody knows of any certain reasons to not scale, but there's plenty of speculation. Someone else posted about Gil Kalai in this subthread, so he's one high profile person that has documented his skepticism on quantum computing and explained his reasons. For my part, I don't think quantum foundations are on a firm footing. I think the measurement problem is still unresolved to a satisfactory degree, which means our understanding of decoherence is incomplete. Per the link I posted above, there's also a good chance that gravity is inherently decoherent, which means entanglement will naturally breakdown in various conditions around mass. I've also developed skepticism of quantum field theories. For one, the supposedly "most precise calculation in physics" has been marred by numerous mistakes and even fraud (electron magnetic moment). Renormalization is also sketchy business. A more fringe reason, but one I think will resolve some of those issues is a growing skepticism of continuity [1], even for classical mechanics; continuous formalisms just seem to lead to logical and physical absurdities, like Norton's Dome and singularities in GR. Discrete theories are only now getting a little attention, but they're promising [2] because they seem to eliminate some of the formal structure (gauges), and the infinities disappear. [1] https://arxiv.org/abs/1609.01421 https://arxiv.org/abs/1609.01421 [2] https://arxiv.org/abs/1902.08997 https://arxiv.org/abs/1902.08997
- klyrs 4y ago
  Here's a well-informed argument to that end: https://arxiv.org/abs/1908.02499 https://arxiv.org/abs/1908.02499 and a nuanced lay-opinion by the same author: https://gilkalai.wordpress.com/2022/05/26/waging-war-on-quantum/ https://gilkalai.wordpress.com/2022/05/26/waging-war-on-quan...
- sampo 4y ago
  > qbits have got massively better over the last few decades Progress has been rather slow: 2001: Shor's algorithm was used to factor 15 2012: Shor's algorithm was used to factor 21 2019: Shor's algorithm was attempted at factoring 35, but failed due to too much error accumulation